There has been a variety of collision detection sensors mounted to a bumper of a vehicle for detecting a collision of a colliding body such as a pedestrian based on a collision load of the colliding body or information associated with the collision load.
A colliding body determination device for pedestrian collision detection described in JP-A-H08-216826 detects a collision of a pedestrian by using a bumper sensor and a hood sensor. The bumper sensor is located between a bumper cover and a bumper absorber for detecting a load applied from a front side in a horizontal direction. The hood sensor detects a load applied from above.
A collision information detector described in JP-A-H07-190732 has a light-emitting circuit section at one end of an optical fiber extending in the horizontal direction and a light-receiving circuit section at the other end of the optical fiber. The collision information detector determines a collision based on a transmission loss of the optical fiber due to the collision.
A vehicle front body structure described in JP-A-2001-39242 has a pedestrian bumper under a front bumper. The pedestrian bumper can protrude forward of the front bumper, suitably laying a pedestrian over a hood in a collision with the pedestrian.
In the real world, there exists a colliding body having a load, which is input into a load sensor in the collision, similar to that of a pedestrian. In addition, the masses of the pedestrians vary (for example, children are light in weight). Therefore, it is not easy for conventional colliding body determination devices to perform the discrimination of the colliding bodies appropriately. The colliding body determination device described in JP-A-H08-216826 can improve pedestrian determination accuracy since the device detects the falling of the pedestrian over the hood. However, the hood sensor cannot transmit an output until the pedestrian falls over the hood after the collision. Therefore, an operable time of a pedestrian protection device after that is very short. Moreover, the device structure is complicated.
In the case where the optical fiber sensor is used as the load sensor, i.e., a sensor for converting a physical quantity associated with a collision force into an electric quantity, as in JP-A-H07-190732, the light-emitting circuit section and the light-receiving circuit section have to be positioned in the right and left ends of the vehicle respectively. Thus, the circuit arrangement is complicated.